package com.nick.job.util;

import org.apache.commons.lang3.Validate;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.beans.factory.DisposableBean;
import org.springframework.context.ApplicationContext;
import org.springframework.context.ApplicationContextAware;


/**
 * 
 * 通过该类快速获取容器中的一些对象
 * 
 * @author dcliu
 * 
 */
public class ContextHolder implements ApplicationContextAware, DisposableBean{
    
    private static ApplicationContext applicationContext = null;
    private static Logger logger = LoggerFactory.getLogger(ContextHolder.class);
    
    /**
     * 取得存储在静态变量中的ApplicationContext.
     */
    public static ApplicationContext getApplicationContext() {
        assertContextInjected();
        return applicationContext;
    }
    
    /**
     * 从静态变量applicationContext中取得Bean, 自动转型为所赋值对象的类型.
     */
    @SuppressWarnings("unchecked")
    public static <T> T getBean(String name) {
        assertContextInjected();
        return (T)applicationContext.getBean(name);
    }
    
    public static <T> T getBean(String name,Class<T> requiredType) {
        assertContextInjected();
        return applicationContext.getBean(name,requiredType);
    }

    /**
     * 从静态变量applicationContext中取得Bean, 自动转型为所赋值对象的类型.
     */
    public static <T> T getBean(Class<T> requiredType) {
        assertContextInjected();
        return applicationContext.getBean(requiredType);
    }

    /**
     * 清除SpringContextHolder中的ApplicationContext为Null.
     */
    public static void clearHolder() {
        logger.debug("清除SpringContextHolder中的ApplicationContext:" + applicationContext);
        applicationContext = null;
    }

    /**
     * 实现ApplicationContextAware接口, 注入Context到静态变量中.
     */
    public void setApplicationContext(ApplicationContext applicationContext) {
        logger.debug("注入ApplicationContext到SpringContextHolder:{}", applicationContext);

        if (ContextHolder.applicationContext != null) {
            logger.warn("SpringContextHolder中的ApplicationContext被覆盖, 原有ApplicationContext为:"
                    + ContextHolder.applicationContext);
        }

        ContextHolder.applicationContext = applicationContext; //NOSONAR
    }

    /**
     * 实现DisposableBean接口, 在Context关闭时清理静态变量.
     */
    public void destroy() throws Exception {
        ContextHolder.clearHolder();
    }

    
    /**
     * 检查ApplicationContext不为空.
     */
    private static void assertContextInjected() {
        Validate.validState(applicationContext != null,
                "applicaitonContext属性未注入, 请在applicationContext.xml中定义ContextHolder");
    }
    
}
